1. What is Length given S is Less than L and Change of Grade?

Definition: This calculator determines the minimum length of a vertical curve when the sight distance is less than the curve length, based on the change in grade and height of vertical curves.

Purpose: It helps civil engineers and road designers ensure proper visibility and safety on vertical curves in road design.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( L_c \) — Length of vertical curve (meters)
• \( N \) — Change in grade (percentage)
• \( SD \) — Sight distance (meters)
• \( h \) — Height of vertical curves (meters, typically 1.7m for driver eye height)

Explanation: The formula calculates the minimum curve length needed to provide adequate sight distance given the change in grade and height difference.

3. Importance of Vertical Curve Length Calculation

Details: Proper vertical curve design ensures driver safety by maintaining adequate visibility, preventing sudden grade changes, and providing smooth transitions between grades.

4. Using the Calculator

Tips: Enter the change in grade (%), sight distance (m), and height of vertical curves (m, default 1.7). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical value for height (h)?
A: The standard value is 1.7 meters, representing average driver eye height.

Q2: When is this formula applicable?
A: This formula is used when the sight distance (S) is less than the curve length (L).

Q3: How is change in grade calculated?
A: It's the algebraic difference between the incoming and outgoing grades (e.g., +3% to -2% is N = 5%).

Q4: What's a typical sight distance?
A: Sight distance varies based on design speed, from 60m for 30km/h to 250m+ for highways.

Q5: What if S is greater than L?
A: A different formula is used when sight distance exceeds curve length.

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